CI: distro releases coverage

[Jakub Ružička]

Hello,

I was pleased to discover BIRD has a very good distro coverage in its
[CI] (~25 different releases).

[CI] https://gitlab.nic.cz/labs/bird/-/pipelines

However, some latest releases are missing so I suggest adding support
for following currently officially supported distros when opportunities
arise:

* Ubuntu 20.04 Focal Fossa - latest LTS
* Ubuntu 20.10 Groovy Gorilla - latest release

* Fedora 32
* Fedora 33 - latest release
* Fedora 34 (optional) is already branched in preparation for release
soon, you can consider enabling it too already

* openSUSE 15.2 (optional)
* openSUSE 15.3 - latest release
* openSUSE Tumbleweed - rolling release (optional)

Also, following distros are either at End of Life or close and can be
removed:

* Fedora 25 - 31 EOL
* Ubuntu 14.04 EOL (16.04 soon)
* Debian 8 is two releases and 6 years old with Debian 11 releasing soon

There is nothing wrong with testing older releases as long as they don't
slow down development by requiring backports and hacks. In such case it
might be a better choice to simply drop support/disable CI for that EOL
distro as opposed to wasting time backporting to dead platforms.


Cheers,
Jakub Ružička
CZ.NIC packager 📦